docs: improve contribution workflow and project governance (#246)

* chore: bump esperanto for anthropic on langchain

* docs: improve contribution workflow and project governance

Implements a comprehensive contribution management system to maintain project quality and vision while welcoming community contributions.

Key Changes:
- Updated CONTRIBUTING.md with clear issue-first workflow
- Added "willing to contribute" checkbox to issue templates
- Created DESIGN_PRINCIPLES.md documenting project vision and principles
- Added comprehensive PR template with quality checklists
- Created MAINTAINER_GUIDE.md with review processes and templates
- Added .github/README.md explaining the contribution flow

Benefits:
- Prevents wasted effort on misaligned contributions
- Maintains architectural consistency
- Provides clear expectations for contributors
- Gives maintainers tools to manage contributions effectively
- Educates contributors on project goals and standards

Related to managing increased community contributions while maintaining project direction.

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -26,6 +26,15 @@ body:
     validations:
       required: true
 
+  - type: textarea
+    id: proposed-solution
+    attributes:
+      label: Proposed Solution (Optional)
+      description: If you have ideas on how to implement this feature, please share them
+      placeholder: "This could be implemented by..."
+    validations:
+      required: false
+
   - type: textarea
     id: additional-context
     attributes:
@@ -35,3 +44,22 @@ body:
     validations:
       required: false
 
+  - type: checkboxes
+    id: willing-to-contribute
+    attributes:
+      label: Contribution
+      description: Would you like to work on implementing this feature?
+      options:
+        - label: I am a developer and would like to work on implementing this feature (pending maintainer approval)
+          required: false
+
+  - type: markdown
+    attributes:
+      value: |
+        ---
+        **Next Steps:**
+        1. A maintainer will review your feature request
+        2. If approved and you checked the box above, the issue will be assigned to you
+        3. Please wait for assignment before starting development
+        4. See our [Contributing Guide](https://github.com/lfnovo/open-notebook/blob/main/CONTRIBUTING.md) for more details
+